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October 07 Octree based engine , First impressionI just completed a basic framework of my engine , which uses octree for occlusion culling and coliision,
You can get the exe file from this link http://cid-a0be50c9af3cc73e.skydrive.live.com/self.aspx/Public/engine%20test/test!.rar
It can render indoor as well as outdoor scenes, Now i think octree are good for suporting coliision detection system , beacuse it can isolate a geomoetry from a complex scene quickly . For occlusion culling octree is ok , but i think it is not enough. The recursion may take longer time than actually drawing the entire area.
I am looking for some other space partioning systems. October 06 Graphics Engine : collision detection using SATCurrently i am working on a graphics engine , which uses loose octree for occlusion culling as well as collision detection..
It works as i am expected. I have implemented the SAT algoritham to test BOX-Triangle intersection test. It works well..
Currently i am checking all the triangles inside the current camera node, It doesn't seems practical with detailes scene.
I need to add support for collision mesh( These mesh are not rendered,they are just used for collision detection).
Hmm.I can see the need for a level editor. Before that i am would like to respond my camera accoring to the geometry in the scene.
Following is the SAT code for triangle - Box intersection , I couldn't find any c++ code in internet ( Muller's is there , it is cryptic for me as well as it is not c++)
template <typename T>
Interfaces3D::InterSection CBBox<T>::IsInsideBox( const Triangle<T>& refTri ) const
{
// If three points are inside the box, definitily the triangle is inside the ABBBox. if( IsInsideBox( refTri.m_Pt1 ) && IsInsideBox( refTri.m_Pt2 ) &&
IsInsideBox( refTri.m_Pt3 ) ) return Interfaces3D::InterSectionIn;
Math3D::vector<T> xAxis(1,0,0);
Math3D::vector<T> yAxis(0,1,0);
Math3D::vector<T> zAxis(0,0,1);
//..............................................................
// Intersection test using SAT (separating Axis test) algorithm.
//..............................................................
float fMin,fMax;
float fBoxMin,fBoxMax;
float fProjTri[3] = { 0,0,0 };
float fProjBox[2] = { 0,0 };
fProjTri[0] = refTri.m_Pt1.x;
fProjTri[1] = refTri.m_Pt2.x;
fProjTri[2] = refTri.m_Pt3.x;
FindMinMax( fProjTri,3,fMin,fMax );
if( (fMin < m_XL && fMax < m_XL ) || (fMin > m_XR && fMax > m_XR ) )
return Interfaces3D::InterSectionOut; // the triangle is outside.
fProjTri[0] = refTri.m_Pt1.y;
fProjTri[1] = refTri.m_Pt2.y;
fProjTri[2] = refTri.m_Pt3.y;
FindMinMax( fProjTri,3,fMin,fMax );
if( (fMin < m_YB && fMax < m_YB ) || (fMin > m_YT && fMax > m_YT ) )
return Interfaces3D::InterSectionOut; // the triangle is outside.
fProjTri[0] = refTri.m_Pt1.z;
fProjTri[1] = refTri.m_Pt2.z;
fProjTri[2] = refTri.m_Pt3.z;
FindMinMax( fProjTri,3,fMin,fMax );
if( (fMin < m_ZF && fMax < m_ZF ) || (fMin > m_ZN && fMax > m_ZN ) )
return Interfaces3D::InterSectionOut; // the triangle is outside.
// Second test is agnist triangles normal.
Math3D::vector<T> vtNormal = refTri.m_Normal;
// project the triangle coordinates on this normal as well as the AABB corners.
Math3D::vector<T> vtRadius = GetTopLeftNear() - GetPosition();
float fExtent = vtNormal.Dot( vtRadius );
float fCenterBox = vtNormal.Dot( GetPosition() );
fProjBox[0] = fCenterBox + fExtent;
fProjBox[1] = fCenterBox - fExtent;
FindMinMax( fProjBox, 2,fBoxMin,fBoxMax );
// projecting triangle coordinates
fProjTri[0] = vtNormal.Dot( refTri.m_Pt1 );
fProjTri[1] = vtNormal.Dot( refTri.m_Pt2 );
fProjTri[2] = vtNormal.Dot( refTri.m_Pt3 );
FindMinMax( fProjTri, 3,fMin,fMax );
// Check for overlapping between pronected coordinates.
// if not overlapping , no intersection.
if( (fMin < fBoxMin && fMax < fBoxMin ) || (fMin > fBoxMax && fMax > fBoxMax ) )
return Interfaces3D::InterSectionOut; // the triangle is outside.
Math3D::vector<T> satAxis[9];
Math3D::vector<T> vTmp = (refTri.m_Pt1 - refTri.m_Pt2);
// edge 0 and X,Y,Z axis
satAxis[0] = vTmp.Cross( xAxis).normalize() ;
satAxis[1] = vTmp.Cross( yAxis).normalize() ;
satAxis[2] = vTmp.Cross( zAxis).normalize() ;
// edge 1 and X,Y,Z axis
vTmp = (refTri.m_Pt3 - refTri.m_Pt2);
satAxis[3] = vTmp.Cross( xAxis).normalize() ;
satAxis[4] = vTmp.Cross( yAxis).normalize() ;
satAxis[5] = vTmp.Cross( zAxis).normalize() ;
// edge 2 and X,Y,Z axis
vTmp = (refTri.m_Pt1 - refTri.m_Pt3);
satAxis[6] = vTmp.Cross( xAxis).normalize() ;
satAxis[7] = vTmp.Cross( yAxis).normalize() ;
satAxis[8] = vTmp.Cross( zAxis).normalize() ;
{
// projecting triangle coordinates fProjTri[0] = satAxis[i].Dot( refTri.m_Pt1 );
fProjTri[1] = satAxis[i].Dot( refTri.m_Pt2 );
fProjTri[2] = satAxis[i].Dot( refTri.m_Pt3 );
FindMinMax( fProjTri, 3,fMin,fMax );
// check for overlapping on the SAT axis
if( (fMin < fBoxMin && fMax < fBoxMin ) || (fMin > fBoxMax && fMax > fBoxMax ) )
return Interfaces3D::InterSectionOut; // the triangle is outside.
}
return Interfaces3D::InterSectionIntersect;
}
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